Texture on large objects are just copying/replicating
The topic of landscape texturing is quite big and not easy to condense to format here. 

Answer 1: 
You aren't using properly tiling texture. When you have properly tiling texture (Texture that has been created/edited to tile/connect to its own border edges) even though it will become repetitive it shouldn't have these sharp edges between the tiles, even at very high tiling. 
(To learn more you should google/youtube "creating tiled textures" or "tiling texture" etc)

Answer 2: 
Even with properly tiling high quality textures using one texture isn't really enough to create a landscape. Using one huge texture map isn't really usually possible either.

What usually happens is that you will have multiple tiling textures blended together in material/shader. So let's say you want to make a grass field with path in the middle. The field might be texture A and the texture you want to use for the path is texture B. Using enough polys on your terrain mesh you could use vertex color painting to paint the path on the mesh. Then in shader/material you would tell that texture A-Vertex color A, texture B-Vertex color B, this way only the area painted with color B would show the path.

Other common technique is to use height to blend materials. So for example you could blend between sand, grass, rock and snow based on height to transition from snowy mountain top, to rocky mountain, to grass lands and finally to a beach. 
Specific workflows for this can be very convoluted based on your platform, though, so again I recommend googling stuff like "material layering workflow" "terrain texturing" and so on. 

I hope some of this was helpful.